1. Field of the Invention
This invention relates to a back-up system for lamps, particularly an electrical back-up system for ballast powered lamps.
2. The Prior Art
Attempts have been made in the prior art to provide emergency or back-up lighting where the normal lighting is supplied by fluorescent lamps and the normal power is alternating current from a commercial utility source.
Examples of such attempts are U.S. Pat. Nos. 4,454,452 to Feldstein (1984) and 4,486,689 to Davis (1984). Both these references teach the use of a hard-to-find emergency lamp in place of a regular fluorescent lamp in which a considerable portion of the lamp tube is taken up by self-contained components such as a battery package and an electrical sensing and switching assembly, leaving but a portion of the tube to house a reduced sized lamp or a series of even smaller lights with consequent diminished lighting power.
These emergency lamps moreover run off a regular ballast which power one or more regularly used lamps, which ballast can burn out i.e. the emergency or standby lamp does not have its own standby ballast.
Accordingly, there is a need and market for an emergency or standby lighting system which employs easy-to-find standard sized ballast-powered lamps and which substantially overcomes the above prior art shortcomings.
There has now been developed a back-up lighting system for ballast-powered lamps which employs standard available lamps and one or more standby ballasts in full scale, back-up lighting.
By "ballast-powered" lamps, as used herein, is meant fluorescent lamps, mercury vapor lamps or high-pressure sodium lamps.